Insecticidal Potentials of Lemon grass (Cymbopogon citratus) Products against Stored Cowpea Weevil (Callosobruchus maculatus) (F) (Coleoptera: Bruchidae)

Abstract

Abstract. Cowpea Weevil (Callosobruchus maculatus), the principal harvest pest of Cowpea, (Vigna unguculata) Order Coleoptera and family Bruchidae is of several economic importance reducing the yield and quality of stored Cowpea. In an attempt to eliminate the menace caused by this insect pest in an environmental friendly way, the insecticidal potentials of Lemon grass (Cymbopogon citratus) products were studied against this insect pest (Callosobruchus maculatus). Sundried fresh leaves of Lemon grass (C. citratus) were pulverized and sieved. The extract was obtained from the pulverized plant part using cold extraction method and ethanol as the solvent. The powder was test at dosage rate of 2.0, 2.5, 3.0 and 3.5g/10kg of experimental cowpea. The insecticidal potential of the extract was evaluated using test tube contact toxicity method at a concentration rate of 0.2, 0.3, 0.4 and 0.5ml/kg of experimental cowpea. Both powder and extract were evaluated for toxicity against C. maculatus at 24, 48, 72 and 96 hours exposure period, with three replicates per treatment. Results indicate that powder had significant difference (P<0.05) in adult C. maculatus mortality. The extract also had significant difference (P<0.05) in adult C. maculatus mortality after 96 h exposure with the highest dose producing 100% mortality. The result reveals that Lemon grass (Cymbopogon citratus) products have potential for use as protection of stored cowpea grains against damage by Callosobruchus maculatus.